A bit of background: I'm 43. My sister is 45. She has always been bossy with me, which I kind of accepted when I was a child even though, naturally, I never liked it.

Since I bought my family home, she has basically harassed me over every decision I've made and tried to put me off or change my mind over it. She was the same over the children. She is very opinionated over how I bring them up and has had something to say over even the smallest things such as breastfeeding, what they have for lunch, how they sleep, their routine, their discipline, their behaviour. Conversely, I have mostly left her alone over her child's upbringing even though it's quite different to the way I bring mine up.

A couple of years ago, she even harassed me over my son's behaviour, aged then 4, saying she thought he had Aspergers because she has a flair for psychology (she is a graphic designer but, hey, who needs a degree now we have google). I even approached his nursery who categorically said he was fine but, according to her, they were still wrong.

I'm in the process of choosing a school for my eldest and to say she doesn't approve of our choice is the understatement of the year. She didn't agree with the fact that I'm involving my daughter in the decision, she doesn't think it's the best for her abilities, she doesn't like the fact that it's single-sex. She has sent me links, proving that she is right, has expressed frustration in that I haven't thought it through and I'm just following everybody else (not true). Recently, my daughter was round her house and even my 8 year old niece was trying to persuade her that the other school is better and BIL even tried to work on my husband. My mum even tried on her behalf and I cut her dead and told her I knew my sister had been talking to her and she couldn't deny it and ended up backing me in the end.

I don't actually need or desire their approval: I simply want to be left alone to make choices for MY child. I feel as if she is not even mine, the way it is going. I don't want to involve the extended family over these kinds of decisions. I feel it should be kept for just the 4 of us. I have been assertive, I think, and tried to set boundaries. She appears to agree then it starts up over again. I am wondering if there is a mental health issue going on because it is very extreme. She admits she is not happily married. Her husband had a psychotic episode and nearly ended up with a bipolar diagnosis but it turned out to be some medication he was one. I'm wondering if there is something going on with her, too.

Short of cutting her off or moving (both discussed with husband), what can I do?

It worked before for a short while when you asserted yourself and set boundariesI suggest you do this again but the minute she tries to slip back inot bossy mode you have to pull her up immediately and say " I don't want to be having that whole conversation we had a few weeks ago so let's end this now"If you do that the first few times she starts up you should be able to stop itShe almost has a habit now and if you let her get away with it she will keep doing itShe is like a naughty puppy who needs a smack on the nose. Puppies grow out of it once smack don the nose enoughI would also point out to her in the conversation that you have thought about cutting her off as this is upsetting you so much. Let her know the consequences of her actions